A conference system is used, for example, in a conference attended by many persons such as an assembly. The conference system is constituted with, for example, a single control unit, a plurality of discussion units connected to the control unit and microphones attached to the discussion units. The control unit manages operations of the discussion units and controls an entire operation of the conference system.
The discussion unit records voice of a user of the discussion unit via the microphone and sends a voice signal thereof to the control unit. The discussion unit is allocated to each participant of a conference.
In the conference system, a participant will make a request for speech to a conference leading person such as a chairperson via the discussion unit. The request for speech is made by one of a manual method in which a user depresses a speech-request button of the discussion unit and an automatic method in which the discussion unit automatically detects speech (voice) of a user to make an automatic voice recognition.
The automatic voice recognition may erroneously detect noise such as sound coming from a desk tapped by a pen or a sound coming from documents handled as voice. In this case, there is made a request for speech which is not intended by a user, thereby resulting in a possible failure that noise spreads across a conference site.
A noise detector in which noise other than voice is not erroneously detected as voice in the automatic voice recognition has been proposed (for example, refer to Japanese Unexamined Patent Publication No. H-6-83391).
The noise (sound) detector disclosed in Japanese Unexamined Patent Publication No. H-6-83391 compares an autocorrelation coefficient of each degree with a threshold, thus making it possible to individually detect silence, noise in a low frequency range (low frequency) and noise in a high frequency range (high frequency).